Currently 65% of the adult population is overweight or obese. Unfortunately, safe and effective treatments for obesity are costly and intensive; therefore, this level of support is unlikely to be feasible in most clinical settings. Moreover, an additional limitation to current obesity treatment approaches is the limited reach and availability of programs for persons who work, live in rural areas or do not want, or cannot afford participation in group support classes. The advent of telecommunications technology may provide a solution to this dilemma. Telecommunications technology can presumably improve access to services and improve efficiency of delivery. Moreover, research examining new technologies such as the Internet, will provide information for policy makers interested in disseminating low-cost, high reach effective obesity treatment interventions. However, the effectiveness of the Internet for inducing weight loss has not been rigorously tested. Therefore, the overall goal of this project is to determine if obesity treatment can be effectively delivered over the Internet. A secondary aim is to evaluate whether the effectiveness of Internet interventions can be improved with the addition of minimal in-person support. Specifically, this project is a randomized, controlled clinical trial designed to test the translation of a behavioral weight loss program to the Internet (1). The I intervention will be compared to both an in-person condition (IP) and an Internet condition supplemented with periodic in-person support (HP). Subjects will be 488 (30% minority) overweight and obese adults recruited from Vermont and Arkansas who will participate in a 6-month behavioral weight control treatment program followed by 12 months of weight maintenance. Assessments will include measures of body weight, adherence to treatment goals, social influence components and frequency of use of Internet website features.